1. Field of the Invention
The present invention relates to duplexers including a first filter and a second filter having different frequency bands, and to circuit modules including a duplexer.
2. Description of the Related Art
To date, for example, a duplexer is formed in such a manner that a transmission filter element defining a transmission filter and a reception filter element defining a reception filter are mounted in a cavity provided in a rectangular ceramic package in plan view, and the cavity in which the transmission filter element and the reception filter element have been arranged is hermetically sealed with a cap. Referring to FIG. 12, a back surface 501 of a duplexer 500 includes thereon a transmission terminal 502 for inputting a transmission signal to the transmission filter from the mounting substrate side of a circuit module in which the duplexer 500 is mounted, and reception terminals 503 for outputting a reception signal from the reception filter to the mounting surface side, a common terminal 504 (antenna terminal) connected to the output side of the transmission filter and the input side of the reception filter, and ground terminals 505.
In the example illustrated in FIG. 12, the common terminal 504 is arranged at a position adjacent to the substantial center of one long side among the two opposing long sides of the back surface 501 of the duplexer 500, and the transmission terminal 502 and the reception terminals 503 are arranged in the corner portions at the two ends of the other long side, thereby substantially forming a V-shaped arrangement. Ground terminals 505 are arranged along the sides of the back surface 501 of the duplexer 500.
It should be noted that FIG. 12 is a diagram illustrating the arrangement of the terminals of the existing duplexer 500. In the example illustrated in FIG. 12, since a reception filter is formed of an unbalanced/balanced-type reception filter element, two of the reception terminals 503 for the reception filter are provided on the back surface 501 of the duplexer 500.
In recent years, mobile communication terminals such as cellular phones and mobile information terminals that support communication based on a plurality of communication standards, for example, the Global System for Mobile Communication (GSM) standard and the Code Division Multiple Access (CDMA) standard, have rapidly become popular. These mobile communication terminals, which perform transmission and reception of signals in different frequency bands using a common antenna, need to have a duplexer that separates a transmission signal and a reception signal having different frequencies for each of the supported communication standards, when communication based on a plurality of communication standards is to be supported. Hence, various front-end modules (circuit modules) that support communication based on a plurality of communication standards have been provided, such as, for example, an antenna switch module in which a switch IC and a plurality of duplexers are arranged on a mounting substrate.
A circuit module that supports communication based on a plurality of communication standards is used in such a manner as to be mounted on a motherboard provided in a mobile communication terminal. In general, the shapes of electrode patterns for mounting a circuit module to be mounted on the motherboard are different among mobile communication terminals. In many cases, the arrangement of mounting electrodes, provided on the circuit module, used for mounting the circuit module on the motherboard is designed for each type of mobile communication terminal in accordance with requests from customers. Hence, the arrangement of a plurality of duplexers 500 on the mounting substrate of the circuit module is also designed in accordance with the arrangement of the mounting electrodes used for mounting the circuit module on the motherboard of the circuit module designed for each type of mobile communication terminal.
For example, there is a case in which two of the duplexers 500, provided in the circuit module, are mounted on the mounting substrate of a circuit module in such a manner that the common terminals 504 neighbor each other in accordance with the arrangement of mounting electrodes connected to the common terminals 504 of the duplexers 500. In this case, since the duplexers 500 are arranged in such a manner as to be point-symmetrical about a rotation point that is the middle point between the common terminals 504, the transmission terminals 502 and the reception terminals 503 of the duplexers 500 are arranged in such a manner as to be point-symmetrical about the rotation point, which is the middle point, i.e., in such a manner as to be arranged spaced apart from each other on the opposite sides of the middle point. As a result, there is a problem in that complex wiring patterns are needed for electrical connection of the duplexers 500 to be provided on the mounting substrate of the circuit module.
Hence, in the example described above, in order to simplify the wiring patterns provided on the mounting substrate of the circuit module on which the duplexers 500 are mounted, it is required, when the two duplexers 500 are mounted on the mounting substrate of the circuit module in such a manner that the common terminals 504 neighbor each other, to arrange the transmission terminals 502 and the reception terminals 503 of the duplexers 500 in such a manner as to be line-symmetrical about a straight line that is parallel with the long sides of the back surfaces 501 of the duplexers 500 and that passes through the middle point, i.e., in such a manner that the transmission terminals 502 of the duplexers 500 are arranged on the same side and the reception terminals 503 of the duplexers 500 are arranged on the same side.
For this purpose, it is necessary to prepare duplexers 500 having different arrangements in which the positions of the transmission terminal 502 and the reception terminal 503 provided on the back surface 501 are exchanged, and to mount the duplexers 500 having different arrangements of the transmission terminal 502 and the reception terminal 503 on the mounting substrate of a circuit module in such a manner that the common terminals 504 neighbor each other. Preparing the duplexers 500 having different terminal arrangements in this manner has caused an increase in the manufacturing cost of the circuit module.